Auto merge of #27006 - ryanp-me:apple-llvm, r=brson
Auto merge of #27006 - ryanp-me:apple-llvm, r=brson

Since Apple LLVM no longer reports which version of LLVM it's based off (starting with 7.0.0), I believe it's time to start checking Apple LLVM versions directly.

The changes in this pull request update the `configure` script to check "Apple LLVM" versions independently if no "based off" version can be found. If a "based off" version is included, however, it will be preferred.

(This is a less hacky version of #26653)

zubron/rust,GBGamer/rust,l0kod/rust,jashank/rust,dwillmer/rust,jashank/rust,GBGamer/rust,zubron/rust,jashank/rust,GBGamer/rust,vhbit/rust,dwillmer/rust,vhbit/rust,zubron/rust,pshc/rust,GBGamer/rust,GBGamer/rust,vhbit/rust,dwillmer/rust,l0kod/rust,jroesch/rust,aidancully/rust,vhbit/rust,aidancully/rust,graydon/rust,dwillmer/rust,nwin/rust,jroesch/rust,pshc/rust,pshc/rust,nwin/rust,jashank/rust,aidancully/rust,jroesch/rust,nwin/rust,nwin/rust,GBGamer/rust,zubron/rust,graydon/rust,l0kod/rust,nwin/rust,dwillmer/rust,graydon/rust,graydon/rust,l0kod/rust,jashank/rust,aidancully/rust,jroesch/rust,zubron/rust,aidancully/rust,jroesch/rust,l0kod/rust,pshc/rust,jashank/rust,jroesch/rust,zubron/rust,dwillmer/rust,pshc/rust,dwillmer/rust,nwin/rust,jashank/rust,nwin/rust,zubron/rust,GBGamer/rust,nwin/rust,graydon/rust,jroesch/rust,l0kod/rust,jashank/rust,zubron/rust,vhbit/rust,jroesch/rust,graydon/rust,vhbit/rust,vhbit/rust,l0kod/rust,GBGamer/rust,l0kod/rust,dwillmer/rust,pshc/rust,pshc/rust,aidancully/rust,vhbit/rust,pshc/rust